libcontainer: user: add tests for numeric user specifications

Signed-off-by: Aleksa Sarai <asarai@suse.de>

libcontainer/user/user_test.go

@@ -101,12 +101,16 @@ func TestValidGetExecUser(t *testing.T) {
 	const passwdContent = `
 root:x:0:0:root user:/root:/bin/bash
 adm:x:42:43:adm:/var/adm:/bin/false
+111:x:222:333::/var/garbage
+odd:x:111:112::/home/odd:::::
 this is just some garbage data
 `
 	const groupContent = `
 root:x:0:root
 adm:x:43:
 grp:x:1234:root,adm
+444:x:555:111
+odd:x:444:
 this is just some garbage data
 `
 	defaultExecUser := ExecUser{
@@ -192,6 +196,26 @@ this is just some garbage data
 				Home:  defaultExecUser.Home,
 			},
 		},
+
+		// Regression tests for #695.
+		{
+			ref: "111",
+			expected: ExecUser{
+				Uid:   111,
+				Gid:   112,
+				Sgids: defaultExecUser.Sgids,
+				Home:  "/home/odd",
+			},
+		},
+		{
+			ref: "111:444",
+			expected: ExecUser{
+				Uid:   111,
+				Gid:   444,
+				Sgids: defaultExecUser.Sgids,
+				Home:  "/home/odd",
+			},
+		},
 	}
 
 	for _, test := range tests {
@@ -206,6 +230,7 @@ this is just some garbage data
 		}
 
 		if !reflect.DeepEqual(test.expected, *execUser) {
+			t.Logf("ref:      %v", test.ref)
 			t.Logf("got:      %#v", execUser)
 			t.Logf("expected: %#v", test.expected)
 			t.Fail()
@@ -218,6 +243,7 @@ func TestInvalidGetExecUser(t *testing.T) {
 	const passwdContent = `
 root:x:0:0:root user:/root:/bin/bash
 adm:x:42:43:adm:/var/adm:/bin/false
+-42:x:12:13:broken:/very/broken
 this is just some garbage data
 `
 	const groupContent = `
@@ -240,6 +266,8 @@ this is just some garbage data
 		"-1:0",
 		"0:-3",
 		"-5:-2",
+		"-42",
+		"-43",
 	}
 
 	for _, test := range tests {